Projection optical system

1. A projection optical apparatus comprising: a projection lens system, wherein some lens elements included in the lens system are disposed so as to be decentered with respect to an optical axis of the entire projection lens system; and a dichroic mirror of which reflecting surface is disposed so as to incline with respect to the optical axis of the projection lens system, said dichroic mirror comprising two transparent substrates and the reflecting surface being formed between the two transparent substrates.

2. A projection optical apparatus as claimed in claim 1, wherein said projection lens system is a non-telecentric optical system.

3. A projection optical apparatus as claimed in claim 1, wherein said reflecting surface of the dichroic mirror is disposed so as to incline 45 degrees with respect to the optical axis of the projection lens system.

4. A projection optical apparatus comprising: a projection lens system; a first dichroic mirror of which reflecting a surface is disposed so as to incline with respect to an optical axis of the projection lens system, said first dichroic mirror comprising two transparent substrates and the reflecting surface formed between the two transparent substrates; and a second dichroic mirror of which reflecting a surface is disposed so as to incline with respect to the optical axis of the projection lens system, wherein a luminous flux of a first wavelength range is rectilinearly transmitted by the first and second dichroic mirrors, a luminous flux of a second wavelength range is reflected at the first dichroic mirror and is rectilinearly transmitted by the second dichroic mirror, and a luminous flux of a third wavelength range different from the first and second wavelength ranges is reflected at the second dichroic mirror, thereby directing all of the luminous fluxes of the first to third wavelength ranges to an image plane, and wherein a plane including optical paths of incidence and reflection of the luminous flux of the second wavelength range on and from the first dichroic mirror and a plane including optical paths of incidence and reflection of the luminous flux of the third wavelength range on and from the second dichroic mirror are orthogonal to each other.

5. A projection optical apparatus as claimed in claim 4, wherein said second dichroic mirror comprises two transparent substrates and the reflecting surface being formed between the two transparent substrates.

6. A projection optical apparatus as claimed in claim 4, wherein said first and second dichroic mirrors are disposed so as to incline 45 degrees with respect to the optical axis of the projection lens system.

7. A projection optical apparatus as claimed in claim 4, wherein said first and second dichroic mirrors have the same substrate thickness and the same angle of inclination with respect to the luminous flux of the first wavelength range.

8. A projection optical apparatus as claimed in claim 4, wherein the projection lens system is a non-telecentric optical system.

9. A projection optical apparatus as claimed in claim 4, wherein some lens elements included in the projection lens system are disposed so as to be decentered with respect to the optical axis of the entire projection lens system.

10. A projection optical apparatus as claimed in claim 4, wherein said first wavelength range is a wavelength range of green (G).

11. A color projector for projecting an image on a display device illuminated by a light source, comprising: a projection lens system for projecting the image on the display device, wherein some lens elements included in the lens system are disposed so as to be decentered with respect to an optical axis of the entire projection lens system; and a dichroic mirror of which a reflecting surface is disposed so as to incline with respect to the optical axis of the projection lens system, said dichroic mirror comprising two transparent substrates and the reflecting surface being formed between the two transparent substrates.

12. A color projector for projecting an image on a display device illuminated by a light source, comprising: a projection lens system; a first dichroic mirror of which a reflecting surface is disposed so as to incline with respect to an optical axis of the projection lens system, said first dichroic mirror comprising two transparent substrates and the reflecting surface formed between the two transparent substrates; and a second dichroic mirror of which a reflecting surface is disposed so as to incline with respect to the optical axis of the projection lens system, wherein a luminous flux of a first wavelength range is rectilinearly transmitted by the first and second dichroic mirrors, a luminous flux of a second wavelength range is reflected at the first dichroic mirror and is rectilinearly transmitted by the second dichroic mirror, and a luminous flux of a third wavelength range different from the first and second wavelength ranges is reflected at the second dichroic mirror, thereby directing all of the luminous fluxes of the first to third wavelength ranges to an image plane, and wherein a plane including optical paths of incidence and reflection of the luminous flux of the second wavelength range on and from the first dichroic mirror and a plane including optical paths of incidence and reflection of the luminous flux of the third wavelength range on and from the second dichroic mirror are orthogonal to each other.